Question : A fair die is thrown 20 times. The probability that on the 10th throw, the fourth six appears is
(A) 20C_{10}\times \dfrac{5^{6}}{6^{20}}
(B) 120×\dfrac{5^{7}}{6^{10}}
(C) 84×\dfrac{5^{6}}{6^{10}}
(D) none of these
Answer : option (C)
Solution :
